Stanford physicists create new form of quantum matter

Research physicists at Stanford University say they have created the world's first "dipolar quantum fermionic gas" from a metal called dysprosium. According to the physicists, the gas represents an "an entirely new form of quantum matter."

Phys.org reports that lead author Professor Benjamin Lev, said the development represents a major step toward understanding the behavior of types of matter made up of strongly interacting fermions that exhibit "unconventional" superconductivity.

According to Stanford University News, when the thermal energy of some substances are dropped below a certain level, the components do not behave as consisting of separate particles. The material becomes "strongly correlated" and begins to exhibit new weird properties.

Technique for cooling gases to near absolute zero was first discovered by Stanford Professor Emeritus Steven Chu, who won a Nobel Prize in 1997. Although researchers later developed more advanced techniques for cooling gases to near absolute zero, they faced technical difficulties in creating "strong correlated" quantum gases.

Professor Lev and his graduate students Mingwu Lu and Nathaniel Burdic, invented a technique involving heating the particles in a crucible to around 1,300 degrees Celsius before shooting them into a vacuum. Using a continuous-wave blue laser, the particles were cooled to within a thousandth of a degree of absolute zero. With further cooling, the gas was brought down to an experimental temperature of 64 nanokelvin, making the gas very, very cold indeed.

Stanford News reports that previous work had concentrated on cooling bosons and weakly magnetic fermions because they are much easier to work with. But the Stanford team worked with a fermionic isotope of dysprosium which has a very strong magnetic field, 440 times stronger than particles that have been successfully cooled.

According to Phys.org, the particles were cooled using an initial step in which they were excited and then allowed to return to their initial states. The particles lost energy in the process and cooled dramatically. Cooling the fermionic isotope of dysprosium was difficult because unlike other particles with two or three energy levels that have been cooled using the same process, dysprosium has more than 140 energy levels.

According to Stanford University News, the second step presented even greater technical challenges. The evaporative cooling process the scientists hoped to use to bring down the gas to the nanokelvin range, depends on collisions between particles. Stanford News reports Lev said: "But the lore in the field is that identical fermions never collide." This is because they obey the Pauli exclusion principle what states that no two identical fermions (particles with half-integer spin) may occupy the same quantum state simultaneously.

The researchers, however, exploited the strong magnetic dipolar interactions between dysprosium atoms to overcome the technical difficulty and cool the particles to below the critical temperature.

Having obtained the sought after "ultracold quantum dipolar fluid," the scientists are hoping to find that the substance exhibits the characteristics of both crystals and superfluids. They are hoping that the apparently contradictory properties will lead to the development of quantum liquid crystals, or quantum-mechanical forms of the liquid crystals found in most electronic displays today. They also speculate that they could yield a supersolid – a hypothetical state of matter that would, in theory, be a solid with superfluid characteristics.

According to Stanford News, the researches have begun developing a "cyrogenic atom chip microscope," a magnetic probe that can measure magnetic fields with "unprecedented sensitivity and resolution." They are also hoping that it may lead to development of a new type of device known as a "topologically protected quantum computer" that supports a more stable form of quantum computation using exotic quantum matter to process information